Hall Book Ch 13 (Cataractogenesis) Flashcards
A cataract is an opacification of the normally transparent lens of the eye.
The progeny of dividing cells in the ( ) of the lens epithelium differentiate into lens ( ) cells. The failure of these cells to ( ) correctly leads to a radiation cataract.
pre-equatorial region, fiber, differentiate
Unique features of the lens include the absence of ( ) in lens fiber cells as well as no mechanism for the removal of dead or damaged cells.
nuclei and mitochondria
The latent period between irradiation and the appearance of lens opacity is ( ).
The latency is about ( ) years after exposure to a dose in the range of ( ) Gy.
dose related, 8, 2.5 to 6.5
It is never possible to state unequivocally that a given cataract is radiation-induced; however, the clinical presentation of a plaque-like opacity at the ( ) in a person with a radiation history strongly suggests radiation as the causative agent.
On the other hand, it is possible to say with some certainty that some cataracts—for example, ( )—do not have a radiation etiology.
posterior lens pole, nuclear cataracts
( ) ions are very effective at producing cataracts. The RBE may be as high as ( ) or more for small doses.
Neutrons or heavy, 50
There is evidence of radiation-associated lens changes in a variety of human populations exposed to low doses of radiation, including the astronaut core, medical workers, A-bomb survivors, accidentally exposed individuals, and those undergoing diagnostic or radiotherapeutic procedures.
Both ICRP (International Commission on Radiological Protection) and NCRP (National Council on Radiation Protection and Measurement) classify a radiation-induced cataract as a tissue reaction (formerly called a ( )) but with a much reduced threshold dose of only ( ) Gy
deterministic effect, 0.5
Occupational exposure limits have been reduced from ( ) mSv per year to ( )
mSv per year averaged over ( ) years, with no single year exceeding ( ) mSv
(ICRP) or 50 mGy per year (NCRP).
1 Sv = 1 J/Kg
150, 20, 5, 50
